The present invention relates to a pressure filter separator. More particularly, the present invention relates to a continuous operation liquid-solids pressure filter separator for use in filtering or dewatering any of various liquid-solids materials to remove the solid components.
Previous internal pressure precoat filters or rotary vacuum filters have typically been constructed in the form of cylinders or cones, in which the filter revolves around an axis, often with cutting blades to cut away precoat and sludge formed inside the cylinder or cone as the precoat becomes impregnated or clogged by filtered solids or sludge. In such prior art filters, the internal pressure which can be applied is limited, due to such clogging, thus increasing the time required to filter a given volume of feed material. Typical of conventional liquid filters of either the pressure, vacuum or free flow type, are those described, for example, in U.S. Pat. Nos. 3,491,889, 3,731,814, 3,322,283, 3,188,942, 3,250,703, 1,212,844, 3,501,004, 2,125,532, 3,762,563 and 3,379,312. A typical backwash filter of the prior art is described in U.S. Pat. No. 3,574,509.
By the present invention, there is provided a pressure filter separator or dewatering device which is constructed so as to provide continuous operation, and which has been found to overcome the above-mentioned disadvantages associated with filtering devices of the prior art.
The pressure filter separator of the present invention is constructed as a cylindrical chamber having a coaxially mounted rotatable wiper blade assembly. A pair of perforated cylinders are mounted outwardly of the wiper blade assembly within the separator in a spaced relationship so as to create therebetween a chamber for filter media and precoat material. A filer media is positioned adjacent the inner surface of the outer perforated cylinder within the chamber created by the inner and outer perforated cylinders. A volume of precoat material introduced into the separator device under the application of either high or low pressure or vacuum is trapped or collected on this filter media. The liquid and solids-containing feed material to be filtered or separated is then introduced into the separator under the continued application of pressure or vacuum and passes in sequence through (1) the inner perforated cylinder, (2) the trapped precoat material, (3) the filter media, and finally through (4) the outer perforated cylinder, after which the filtrate collects in an outer collection chamber for subsequent removal. The blades of the wiper assembly could feasibly touch the surface of the inner perforated sleeve, however to prevent wear on the surface of the sleeve and the outer edge of the wiper blades there will be a preferred clearance of 1/64 to 1/16 inch between the wiper blades and the surface of the inner perforated sleeve. The constant movement of the wiper blades in close proximity to the surface of the inner perforated sleeve maintains the inner surface of said sleeve free of solid material except for the slight residue of 1/64 to 1/16 inch which will not appreciably impede the passage of filtrate through the perforated sleeve into the precoat chamber.
At no time do the rotating wiper blades make contact with either the filter media or the precoat material which has been trapped by the filter media, so that there is possibility of wiping or "blinding" of the filter media. Also, due to the fact that the filtering process is constant, there is no necessity for a backwash procedure. The combination of the pressure applied to the feed material and the action of the rotating wiper blades forces the sludge or filtered solids to the center of the separator, where such solid material is removed by a valve shaft arrangement which includes three concentric shafts constructed of hollow piping. Valve action is provided by controlling, through pre-determined positioning, the relative location of vertical and spiral slots cut into the three shafts.
A primary advantage of the present invention resides in the fact that higher filtration pressures may be employed than is possible with conventional filter devices, thus substantially reducing the time required to filter a given volume. In addition, dewatered solids or sludge may be removed at varied rates and compositions as desired, by operation of the concentric valve shaft arrangement of the present invention. As used herein, the term "sludge" includes typically a suspension of solids in a liquid such as water.